1. Technical Field
This patent application is related to intensity modulated fiber optic sensors, and more specifically, to fiber optic sensors for measuring temperature.
2. Related Technology
In recent years, optical fibers have formed the basis for many different types of sensors, such as microphones, static and dynamic pressure sensors, strain sensors, among others. Optical fiber sensors can use interferometry or intensity modulation. Intensity modulated fiber optic sensors, while often less sensitive than comparable interferometric sensors, are simpler and less expensive.
An interferometric fiber optic temperature sensor is disclosed in Aref, S. H., Zibaii, M. I., and Latifi, H., “An improved fiber optic pressure and temperature sensor for downhole application”, Meas. Sci. Technol., Vol. 20, pp. 034009 (February 2009). Another interferometrically-based fiber optic temperature sensor system is described in Huang, Z., Peng, W., Xu, J., Pickrell, G. R., and Wang, A., “Fiber temperature sensor for high-pressure environment”, Optical Engineering, Vol. 44, No. 10, pp. 104401-1-104401-6 (October 2005).
The theory of intensity modulated optical fiber sensors, including pressure sensors and microphones, and examples of such sensors, are disclosed in U.S. Pat. No. 7,379,630 to Lagakos et al., U.S. Pat. No. 7,020,354 to Lagakos et al., and U.S. Pat. No. 7,460,740 to Lagakos et al. U.S. Pat. No. 7,149,374 to Lagakos et al. discloses fiber optic pressure sensors having an etched diaphragm, and methods for forming the diaphragm. U.S. Pat. No. 7,646,946 to Lagakos et al. discloses intensity modulated fiber optic strain sensors. The entire disclosures of these documents are incorporated herein by reference.
A temperature sensor using optical interferometry with a bimetallic membrane and an optical fiber source is discussed in Yueming, L. Xiaoqiang, Z, and Shaojun, Z, “Novel temperature sensor based on Fabry-Perot cavity structure and micro-mechanical bi-layered membranes”, SPIE Proceedings, Vol. 6032, DOI:10.1117/12/667855, 7 pages, February 2006.